1. Field of the Invention
The present invention relates generally to concrete and more specifically to a new ultrahigh performance concrete (UHPC) composition and a process of preparing it.
2. Description of Related Arts
Concrete is widely used in the construction industry because it is economical, ubiquitous, and durable with considerable compressive strength. In previous arts, without large aggregate in UHPC formulations, achieving sufficient shear in mixing is a challenge. With only fine particles composition, the existing state-of-the-art UHPC slurry is relatively viscous, requiring a costly upgrade from existing drum mixer to high-viscosity specialized mixer that has smaller production quantities but more energy consumptions to produce it.
Furthermore, transportation and placement of UHPC has challenges. The curing treatment applied to concrete with steam treatment requires a controlled environment, which may not always be feasible in field pouring conditions.
U.S. Pat. No. 8,303,708 issued to Lafarge presents a ductile UHPC. Lafarge attempts to optimize packing theory by paying careful attention to granular sizing variables and achieving a consistent production quality. This strict sizing and quality control severely limits the available locations where the constituents can be sourced, which means formulation adaption of local materials is prohibitively expensive and laborious.
Instead of formulation adaption, Lafarge's UHPC material is shipped remotely to jobsites with multiplied costs. Facing difficulties in transporting large UHPC-structures, Lafarge markets its UHPC instead as joint fill with better success compared to efforts in mass-distributed mainstream applications.
Besides the aforementioned drawbacks, i.e., strictly-sourced fine particles only, costly equipment upgrades, and high-shear slurry, production time is also multiplied. Known prior arts also focus on the choice of conventional fibers, namely, made of steel, glass, polypropylene, and/or PVA (polyvinyl alcohol) which are often proven to be undesirable. Moreover, the conventional fibers are less physically compatible to concrete or poor in handling high pH.